Hydrocolloid adhesive compositions have been known for many years. Chen, in U.S. Pat. No. 3,339,549 discloses a blend of a rubbery elastomer such as polyisobutylene and one or more water soluble or water swellable hydrocolloids such as a powdery mixture of pectin, gelatin and carboxymethylcellulose. The adhesive mass has a water-insoluble film applied to one surface. A composition of this type is available commercially from E. R. Squibb & Sons Inc. under the trademark "Stomadhesive" and is used as a skin barrier around stomas to prevent skin breakdown by the corrosive fluids discharged by the stoma.
In hydrocolloid adhesive compositions of this type, the polyisobutylene provides the adhesive properties and the dispersed hydrocolloid powders absorb fluid. These compositions are gaining increasing acceptance as wound dressings for dermal ulcers, burns and other exudative wounds.
One major problem which has been encountered with conventional hydrocolloid adhesive compositions is their susceptibility to breakdown upon exposure to wound exudate and body fluids. When the compositions are used as skin barriers, e.g., around stomas, absorption of fluid is desirable, but excessive swelling causes the composition to lose its moisture seal with the skin. Leakage occurs and the barrier must be replaced more often than is desirable.
Conventional hydrocolloid compositions used as wound dressings in the treatment of, for example, burns, dermal ulcers and pressure sores tend to dissolve upon exposure to wound exudate and form a gel on the surface of the wound. When the dressing is removed, a residue remains on the wound requiring removal, typically by irrigation. When this breakdown occurs the dressings may also lift off the wound and allow leakage of wound exudate onto clothing and bedding.
A number of attempts have been made to improve the integrity of hydrocolloid compositions.
U.S. Pat. Nos. 4,192,785 and 4,551,490 describe incorporating into the hydrocolloid composition a cohesive strengthening agent such as natural or synthetic fibrous material, finely divided cellulose, crosslinked dextran, crosslinked carboxymethylcellulose or a starch-acrylonitrile graft copolymer. The cohesive strengthening agent is said to control the rate of hydration of the composition thereby increasing resistance to breakdown by body fluids.
U.S. Pat. No. 4,477,325 describes incorporating into the hydrocolloid composition a mixture of a copolymer resin of ethylene and vinyl acetate (EVA). After mixing and molding, the composition is subjected to ionizing radiation to form crosslinked polymer networks of the EVA or EVA with another crosslinkable resin. The crosslinked matrix is said to provide controlled swelling.
U.S. Pat. No. 4,496,357 describes the incorporation of fumed silica into hydrocolloid compositions to control swelling.
Generally speaking, these prior methods of improving the integrity of hydrocolloid dressings all involve crosslinking or otherwise strengthening the matrix of the composition to control swelling upon contact with body fluids. This approach tends to limit the absorption capacity of the composition, which is not always desirable, particularly when the composition is used as a wound dressing on highly exudative wounds.